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Point electrics

I've got a Marcway point with continuous blade and live frog.

The problem is that the two innermost of rails of the two diverging tracks, which are joined together at the frog, have lost electrical connection with the blades and hence with input feed (it's a mechanical issue - press lightly on the frog and power is restored). So I want to drop a feeder wire down and back up again, which leads me to Q1: does it just need to connect with either of the blades?

And Q2: am I correct in thinking that on all these points, electrical conduction is simply through the blades touching the fixed rails? And thus a mechanical switch under the board is a wise backup?

R.

Reply to
Richard
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Richard

Not familiar with Marcway points, but live turnouts conventionally have the whole crossing assembly (ie the 'frog' and the adjoining closure and diverging rails) as a self-contained unit which is isolated* from everything else around it but electrically bonded internally. (* The assembly is then switched to the polarity required depending on the setting of the points).

I wouldn't rely on blade contact for electrical connection. Again, the convention is for the blades and the adjacent stock rails to be electrically bonded.

Hope this helps rather than confuses, but you might want to take an ohm-meter across the various component rails in each point position to see what is going on before proceeding (and recheck as you go).

Cheers Rod

Reply to
Roderic Cameron

A1: Since only one blade at a time contacts the stock rail, it would need to be connected to both.

A2: If the frog is isolated from the blades, you can use a microswitch or relay activated by the point motor to switch the frog polarity.

Reply to
MartinS

"MartinS" wrote

It appears from the symptoms described, that the soldered joint under the vee has failed but that the joints under the adjacent wing rails are still ok, such that both switch rails form a single electrical unit by way of the copper topped sleeper passing under the vee.

I'd attempt to resolder the joint but I can understand that not all modellers would want to try this as there is some risk of the whole thing falling apart.

An alternative might be to use conductive paint but I'm not sure that I'd want to trust this myself.

Reply to
Terry O'Brien

I recently bought some conductive epoxy from an electronics dealer but haven't tried it yet. It claims to make as good a mechanical and electrical bond as solder, and it would avoid the problem of melting plastic sleepers when connecting rails or adding feeder wires.

I have a similar problem with Hornby points in which the diverging rails do not make good contact with the piece on which the blades swivel.

I considered the conductive paint in conjunction with regular epoxy or superglue, but decided against it.

Reply to
MartinS

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